Tailgates for pickup trucks typically range in weight from 40 to 60 pounds and are hinged at the rear of a truck bed such that when the tailgate is unlocked by the pulling of a lever or handle, the tailgate opens to a point level with the truck bed where it is restrained, usually by detachable folding straps. Typically, the tailgates can be removed from the truck body when the tailgate is pivoted to a partially open tailgate removal position.
The weight of the tailgate precludes one handed operation for any but the strongest individual. People of normal build have to use their second hand, shoulder or knee to raise the tailgate or to support the tailgate in an effort to keep it from dropping too quickly. Often it is the case where an individual opening a tailgate will only have one free hand, thus causing a strain in the wrist of the individual as the wrist must bear the weight of the tailgate.
Normally a person drops the gate or sometimes raises his or her knee in order to arrest the fall of the tailgate. By so doing, the individual has a chance of being injured if the tailgate falls on the knee by this process. The raising of one's knee to prevent the tailgate from dropping has reportedly resulted in crushed knee caps or other damage to the knee. It will be appreciated that a free falling tailgate can, in fact, crush anything that is underneath it and can, for instance, hurt children who are standing at the back of the tailgate when it falls.
One common solution to counterbalancing the weight of the tailgate is by the use of a torque rod that is fixed to the tailgate at one end and coupled to the truck body at the other end (U.S. Pat. No. 5,358,301, US2005/0194808A1 et al).
Dampers have been employed to achieve a controlled rate of descent. One solution utilizes a spring with viscous damping that is mounted between the tailgate and the truck body and controls the motion of the tailgate with a bell crank and an actuation shaft (U.S. Pat. No. 6,773,047 B2). Another attempted solution has been a power tailgate installation described in U.S. Pat. No. 6,357,813 that consists of a motor mounted on the truck that actuates the tailgate by a crank arm and a sliding component.